A compact disc may be formatted to include compressed audio content, such as MP3 files or any other suitable compressed audio format. In the case of the MP3 compressed audio format, as many as 400 music files or songs can be placed on a single compressed audio CD. A CD that includes compressed audio files can be played on a CD player that is configured for the playback of compressed audio files formatted on a CD disc. CD players of this sort include CD-ROM players and hybrid CD players that can play both traditional CDs and CD-ROMs that include compressed audio files. Regardless of the particular compact disc format, CDs that includes compressed audio files are referred to herein as compressed audio CDs.
A CD that includes compressed audio files typically includes a file system. Conventional audio CDs do not include a file system. Instead, conventional audio CDs include directory information that is arranged sequentially on the CD. In contrast, the file system of a CD that includes compressed audio files is somewhat detailed and is arranged logically in the form of a tree data structure. The tree data structure of a compressed audio CD includes a root directory. A number of files or file folders can be placed on the root directory, with each file folder comprising a directory for a number of other files and file folders. The folders of the directory tree of the CD can be used to group individual files or songs on the basis of the artist of the selection, the album of the song or musical selection, or the type of song or music selection. This file system may be arranged according to the preferences of the user and may be unique to each CD to be played by the CD player.
When a CD having compressed audio data is inserted into a CD player that is configured to play the compressed audio content, the CD player typically reads the file system data of the CD and saves information from the file system of the CD to the memory of the CD player to create a file system in the memory of the CD player. The file system of the CD player is used by the CD player to locate MP3 files or other compressed audio files on the CD and to identify the logical and nested relationships between these files and the folders that contain these files on the CD. Building a file tree, which is the data structure of the file system saved to the memory of the CD player, is advantageous because it provides a quick guide for accessing the contents of the CD and obviates the need to access the file system information that is saved on the CD.
Building the file tree in the memory of the CD player from the file system data on a compressed audio CD is often a time-consuming process. The file system data on the CD disc is not arranged as sequential data. Rather, the file system data is encoded onto the disc in the form of a logical tree. Because of the format of the file system data on the CD, the CD player must make a number of seeks or jumps to locations on the CD to read in the required file system data. Seeks, however, are time-consuming. In part because of the delay introduced by the number of seeks required to build the file system of the CD, as many as ten seconds or more may elapse between the time that a user inserts a CD in the player and the playback of the first selection on the CD. This delay is unacceptable, as users of standard CD players are typically accustomed to playing a CD within one to two seconds of placing the CD in a standard CD player.